1818] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



SS 



is 30 tons. The axis of the dnim is of wroupht-iron, 12 inches 

 diiimeter in the bearings. The cogs of tlie mortice-wheel are 

 marie of hornbeam. 



The break is formed of two straps of wrought-iron, side by side, 

 each 5 inches wide, to which are rivetted plates of copper in 

 lengths of 3 feet each, 12 inches wide and | inch tliick ; tlie copper 

 applies to the lower half of the circumference of tlie break-wlieel. 

 One of the extremities of the break is suspended by rods from 

 the girder above, and the otlier end is connected to the hoop 

 around an eccentric-wheel, tlie axis of which is mounted in a frame 

 fixed to the girder. On the axis of this eccentric-wheel is a spur- 

 wheel, into which a pinion works, and on the axis of the pinion 

 is a ratchet-wheel, to be worked by a lever-handle and click, by a 

 man standing on the platform over the engine-room, the handle 

 end of the lever passing up through tlie platform. The length of 

 this lever-handle is 6 feet; the diameter of the pinion is 11^ 

 inches, and that of the wheel is 16 inches ; the eccentricity of the 

 eccentric-wheel is 2| inches. Hence the force of the man's arm 

 applied at the upper end of the lever-handle is multiplied about 



36 times ( = 3G-4,| when the leverage is the least — 



\2'75 X 11-5 '/ ^ 



namely, when the eccentric-wheel has made a quarter of a revo- 

 lution ; but for obtaining a greater power on the break, a piston 

 is fitted into an air-cylinder 10 inches in diameter, which is fixed 

 under the girder ; one end of the cylinder is open to the at- 

 mosphere, and the other is closed, but communicates by a pipe 

 with the condenser of the steam-engine below. In this pipe is a 

 cock, wliich can be opened by the lu'eaksman when necessary ; a 

 chain connected to the rod of the piston of the air-cylinder, is 

 carried round the spur-wheel and fastened to it. If the breaks- 

 man opens the cock to establish a communication with the con- 

 denser, the air is exhausted from the air-cylinder, and the pressure 

 of the atmosphere on the area of the piston acts by the chain on 

 the circumference of the wheel. Supposing the vacuum to be 27 

 inches of mercury, this pressure is l,060lb., equivalent to about 

 lOOlb. applied to the upper end of the lever-handle. 



Each of the moving plumnier-blocks, in which the drum-shaft 

 revolves, is mounted on six rollers ; three on each side. Beneath 

 the plummer-blocks and attached to it, in the space between the 

 rollers, is a long nut in which a screw 3 inches in diameter works ; 

 the pitcli of this screw is such as to move the nut and the 

 plummer-block 3 inches by seven revolutions. The axis of the 

 screw is prolonged by a sliaft to reach the platform, and this pro- 

 longation has on its end a bevil-wheel 2 feet in diameter, into 

 which works a bevil-pinion 6 inches in diameter ; the cross axis of 

 this pinion extends across the breadth of the drum, parallel to its 

 axis, and carries another such bevil-pinion of 6 inches diameter, 

 which acts in another bevil-wheel of 2 feet diameter, on the pro- 

 longation of the axis of another screw beneath the plummer- 

 block, for the other end of the axis of the drum. By this con- 

 nection both screws are turned round simultaneously and act on 

 both plummer-blocks alike. On the cross axes of the two bevil 

 pinions is a cog-wheel 2 feet in diameter, into which works a 

 pinion 16 inches diameter, on the axis of which is a winch-handle, 

 so that to produce one revolution of the screw, the winch-handle 

 must make six revolutions. Tlie thread of the screw making seven 

 turns in 3 inches, and the winch being 10 inches long, the pressure 

 applied to it is multiplied 868 times. The winch is worked by one 

 man, and the time occupied in disconnecting one drum and con- 

 necting the other, is little more than a minute. 



The rollers on which each plummer-block moves, are made of 

 wrought-iron, case hardened, 3^ inches in diameter, and 2g inches 

 broad. At first, the rollers worked against the cast-iron surfaces 

 of the frame and of the plummer-block ; but after having been at 

 work two or three years, the pressure had caused so much inden- 

 tation into the two surfaces of cast-iron, as to render it difficult 

 for a man to connect and disconnect the large spur-wheels. To 

 remedy this defect, a strap of steel was let into the frame and 

 another into the underside of the plummer-block for the rollers 

 to act against, and no inconvenience has been since found. The 

 weight upon each of the rollers is about 5 tons. The weight of 

 the drum, break-wheel, and mortice-wheel being 30 tons, and of the 

 a.xes 3 tons 7 cwt., the rope remaining on the drum when unwound 

 1 ton, and the additional weight of rope wlien the whole is wound 

 an, 23'10 tons, makes a total weight of 57-17, or 58 tons, to be 

 sustained on the twelve rollers beneath the two plummer-blocks; 

 and, therefore, supposing each set to bear the same weight, each 

 roller has to carry neai-ly 5 tons ; each end of the axis of the 

 drum being 12 inches diameter in its bearing, the breaks must 

 sustain 29 or 30 tons. 



Power. — Wlien all the train is in motion, the engines making 

 22 strokes per minute, the pressure of the steam on entering the 

 cylinder being 2^ lb. above that of the atmosphere, and the mean 

 pressure 9-95 lb. per square inch, the power for the engines, rope, 

 and train, is 323-74 horse-power. 



When the rope, without any carriages attached to it, is drawn 

 by the engines making 2t revolutions per minute, the pressure of 

 the steam being 6 lb. above the atmosphere, and the mean pressure 

 7 lb. per square inch, the power expended on the rope and ma- 

 chinery is 25076 horse-power. 



When the drum is disconnected from the engines, and they are 

 allowed to make 22 strokes, the pressure being 13i lb. abo\e the 

 atmosphere, and the mean pressure 8lb. per sq'uare inch, the 

 power expended on the friction of the engines unloaded, is 26-09 

 horse-power. 



Since the power expended on the engines, rope, and train, is 

 323-74 horse-power, and on the engines and rope, 250-76 liorse- 

 power; the difference, namely, 72-98 or 73 horse-power is due to 

 the train alone. 



The number of revolutions made by the engine-shaft per minute 

 being 22, the number made by the drum in the same time is 33-84. 

 The circumference of the drum w hen the rope is oft', is 52 feet ; 

 when all the rope is wound on, it is G3 feet, the velocity of the 

 rope will therefore vary from 1,760 feet per minute, to 2,i32 feet, 

 that is, from 20 miles to 24 miles per hour. 



TheRope. — When the railway was first opened, the rope employed 

 was of hemp, 5| inches in circumference, or if inches in diameter. 

 After it had been in use for a very short time it broke, and con- 

 tinued to do so frequently ; in consequence of which, a wire rope 

 was substituted. This rope 3g inches in circumference, or 1^ inch 

 diameter, is formed of six strands, each composed of six wires, or 

 thirty-si.x wires in the rope. It is covered over vvith small hempen 

 rope or tarred yarn. The breakages of this rope are much less 

 frequent than with the hempen rope, but still they do occur occa- 

 sionally. In order to make the rope wind evenly on the drum, it 

 is guided by two levers mounted on one centre pin, and crossing 

 one another in the form of a pair of scissors, the levers having 

 rollers on their inner side. These levers are worked by a man, 

 standing on the platform below, and he guides the rope by pressing 

 them alternately against either side as his eye directs, so as to 

 wind the rope evenly around the drum. 'The weight of the 

 hempen ro])e was 8 lb. per yard, tliat of the wire rope is 65 lb. per 

 yard ; therefore, the weight of the rope lying on the railway was, 

 in the former case, 19,; tons, and in the latter, 16^ tons. Swivels 

 are introduced at inter\als in the length of the rope, to allow it to 

 twist and untwist itself in working. The weight of the rope is 

 sustained by bearing-sheaves, disposed at intervals along the line, 

 in the middle of the space betw een the rails ; some of them being 

 laid at angles to suit the curves of the road. 



The auxiliary engine. — The cylinder of the 12 horse-power 

 engine is 20 inches in diameter, the piston makes a stroke of 

 3 feet, and 34 strokes per minute. The two air-pumps which are 

 worked by it are 13 inches in diameter, with a stroke of 10^ 

 inches, and are placed one on each side of the centre of the main 

 lever. 



The air-pumps of the large engine are 31 inches in diameter, 

 with a length of stroke of 2 ft. 6 in. ; so that the capacity of the 

 stroke of each pump is 13-1 cubic feet, or 26-2 cubic feet for the 

 pumps of a pair of engines ; therefore, the capacity per minute, 

 is S6-2 X 22 strokes = 576-4 cubic feet. In like manner, the ca- 

 pacity of the small pumps, per minute, is 55 cubic feet, or nearly 

 iTjth that of the large pumps in the same time. 



The well, from which cold water is obtained is 10 feet diameter 

 inside, and is steined partly with brick and partly with iron. In 

 this well are two sets of three-barrelled pumps, but only one set is 

 worked at a time. The barrels are each 7 inches in diameter, the 

 stroke is 18 inches, and they make twenty strokes per minute ; so 

 that the quantity of water raised by one set, per minute, is 150 

 gallons. 'These pumps are worked constantly throughout the day. 



The marine-boilers are 10 ft. 3 in. wide, 10 ft. 8 in. high, and 

 24 feet long ; the steam-chests are 5 feet in diameter and 4 ft. 

 10 in. high; each boiler has three fires within it. 



The circular boilers are each 7 ft. 6 in. in diameter, by 24 feet 

 long ; the two circular flues, through their whole length are 2 ft. 

 6 in. diameter. The steam chests are 3 ft. 9 in. diameter, and 4 feet, 

 5 feet, and 6 feet high respectively. The average consumption of 

 fuel, is, per day, for the two marine-boilers together, 7g tons, and 

 for the three circular-boilers together, 8 tons. In these quantities 

 is included what is required for getting up the steam in the morn- 

 ing. 



